The invention relates to a method for the automated actuation of a clutch in the drive train of a motor vehicle equipped with a drive motor and gearbox and to a device for this purpose.
Methods and devices of this kind for clutches which can be actuated automatically are known for example from DE 44 26 260 or DE 195 07 847. With automated clutch systems of this kind the actuation of the clutch is undertaken automatically by means of an actuator and the clutch pedal can be omitted. The driver of the vehicle equipped with an automatic clutch of this kind can influence the automated clutch actuation for example by operating the drive pedal, such as the accelerator.
Where a stretch of the road is inclined it is now possible for the vehicle to be held stationary or substantially stationary with a slight actuation of the drive pedal by the driver through corresponding engagement of the clutch, since the torque transferred by the clutch through the control using the actuation of the drive pedal is sufficient to hold the vehicle on the slope against the downhill output force. Also driving is possible with very slight actuation of the drive pedal whereby the clutch constantly slips at low drive speed over a longer time.
In the event of longer or repeated slipping states at low drive speed or with stationary states of the vehicle on a hill or even with numerous repeated even short stopping states this can lead to the clutch rapidly wearing out prematurely. There is also the problem that the driver of the vehicle as a rule has no knowledge of the increased wear on the clutch.
The object of the invention is to detect critical stopping states of the vehicle when the clutch is partly engaged, for example on a slope or longer slipping states and to alert the driver of a situation which is critical for the service life of the clutch and/or to initiate remedying measures.
According to the invention this is achieved by a method for the automated actuation of a clutch in the drive train of a motor vehicle equipped with a drive motor and a transmission, with a device for the automated actuation of the clutch with an electronic control unit and actuator for actuating the clutch, with a drive pedal for controlling the drive motor, in that the following steps are carried out:
detecting a transmission speed n of substantially zero or less than a threshold value;
detecting a measurement of drive pedal actuation x which is not equal to zero and less than a predeterminable threshold value;
with the presence of these conditions initiating warning measures to alert the driver to a misuse situation and/or remedying measures.
Through this overall combination of a transmission speed of substantially zero or less than a predeterminable threshold value and a drive pedal actuation on the part of the driver within a predetermination actuating range which is other than zero and less than a predeterminable threshold value a stopping situation on a hill or a very slow drive speed of the vehicle with the clutch slipping is detected. A warning or remedying measure can then be initiated.
According to the invention the object can also be achieved if the following steps are carried out:
detecting a slip which is greater than a threshold value;
detecting a measurement of the drive pedal actuation x which is other than zero and less than a predeterminable threshold value;
with the presence of these conditions initiating warning measures to alert the driver to a misuse situation.
The above definition of slip is to mean the difference between the engine speed and the gearbox speed wherein the engine speed can be determined by means of an engine speed sensor and the gearbox speed can be determined by a gearbox speed sensor or by calculations using a wheel speed. The condition of the slip greater than a threshold value means that with a given engine speed the driving speed with a slipping clutch is very low which results in increased wear of the clutch. The threshold value for the slip can be for example at about 300 1/min to 700 1/min, such as preferably 500 1/min, so that warning measures and/or remedying measures are controlled when the difference between the engine speed and gearbox speed exceeds this value , provided that other conditions also exist. It is advantageous if the threshold value for the slip is below the value of the idling speed of the engine.
According to a further inventive idea the object of the invention is also achieved in that the following steps are carried out:
detecting a gearbox speed n greater than a threshold value
detecting a measurement of a drive pedal actuation x which is other than zero and less than a predeterminable threshold value;
with the presence of these conditions warning measures are introduced so that the driver is alerted to a misuse situation.
According to the invention it is expedient if for actuating the drive pedal a range is provided which is greater than nil and smaller than a predeterminable threshold value. This is therefore expedient because it is not advisable to initiate warning measures if the accelerator pedal is not activated or even to engage the clutch if the accelerator pedal is not activated. It is also expedient to rule out the full throttle area since with full throttle a warning is less advisable since the driver deliberately carries out this maximum drive pedal actuation.
It is accordingly expedient if the drive pedal actuation according to the invention is in the region from 3% less than x less than 75%.
It is thereby advantageous if the gearbox speed n is greater than a predeterminable threshold value, thus for example 500 1/min. It is particularly advantageous if the threshold value of the gearbox speed is below the idling speed of the drive motor.
It is thereby expedient if the measurement x of the drive pedal actuation can be detected by means of a drive pedal sensor.
It is also advantageous if a drive pedal actuation x which differs from zero can be detected by means of an idling switch.
According to the invention it is expedient if the speed is determined by means of a gearbox speed sensor. It can also be expedient if the speed is determined by means of a wheel speed sensor taking into account the gearbox transmission ratio and where necessary a drive train transmission ratio.
According to the invention it is expedient if the slip is determined as a difference between an engine speed and the gearbox speed from values of the engine speed and a gearbox speed. The engine speed can thereby be determined for example from an engine speed sensor and the gearbox speed from a gearbox speed sensor or can be determined from a wheel speed by means of the transmission ratio of the gearbox and the drive train transmission ratio.
According to the inventive idea it is expedient if the warning measures are produced immediately after the existence of the conditions which are necessary for same. It can also be expedient if the warning measures are produced only after the lapse of a waiting time after the existence of the conditions which are necessary for same. It can also be expedient if the warning measures are produced after the existence of the conditions required for same and a clutch temperature which is raised beyond a threshold value. In this respect reference is made to DE 196 02 006 whose contents are expressly included in the disclosure of the present application documents.
An advantageous warning measure according to the invention can be produced through control of an optical indicator, such as a warning light coming on, or a warning light flashing or a gear display.
The warning measure can also be introduced in advantageous manner through a control which produces an acoustic signal such as a warning tone.
Furthermore it is expedient if the warning measure or remedying measure is initiated when the clutch is engaged.
It can also be expedient if a warning measure is initiated through a controlled at least partial engagement or disengagement of the clutch so that the drive train is caused to pulsate.
The invention further relates to a device for an automated clutch for carrying out the method described above.